How to cut G10 fins?

[ScrapDaddy]

Hi people I am compleatly new to the idea of scratch buoliding with composites Besides asking PML to do it (they have a minimum size) and sending it off to commonwealth displays so they can cut the stuff with their laser cutter (does that even work with G10?)do you guys have any household tips that don't require a power tool?

 

[ScrapDaddy]

These are all straight lines(no elipoid fins yet!)

 

[GregGleason]

I am pretty sure you cannot cut G-10 with a laser cutter. You have to use carbide tips on the saws.

https://www.vernk.com/Construction/StarfireFinCan.htm

Greg

 

[The EGE]

I am pretty sure you cannot cut G-10 with a laser cutter. You have to use carbide tips on the saws.

https://www.vernk.com/Construction/StarfireFinCan.htm

Greg

There are things that cannot be cut with industrial lasers? My mind, it is blown.

 

[MattieShoes]

The real question is Will it blend?

More seriously, don't try to wing it. G10 is fiberglass. You really don't want to inhale the dust. REALLY. People that do this stuff wear respirators, or at least should be.

 

[Gillard]

a laser cutter will cut G10. It won't cut metal or anything that reflects light (obvious if you think about it)
G10 however, produces alot of smoke and mess with a laser cutter.
i cut my G10 with a band saw and have not had any problems yet.

 

[GregGleason]

a laser cutter will cut G10 ...

Yes, that is correct.

I should have been a little more precise in my post, which I will now do.

Will a laser cut G-10? Yes.

Will a laser cut G-10 as nicely and cleanly as it does wood? Absolutely not.

I have an acquaintance who has a laser cutting business and I ask him to cut a sample of 0.125" thick G-10 that I had. While it did cut, the edges were burned/charred and did not look pretty at all. And there was the smoke it caused. From our conversation after the fact, it was apparent to me that cutting G-10 was an event he wouldn't care to repeat.

So from a practical standpoint, the answer is no. Best to go with other tools AND where a respirator, not just a dust mask.

Greg

PS: This was a couple of years ago so there may be next generation laser cutters out there that can cut G-10/FR4 material well.

 

[troj]

How thick is the G10 you want to cut? As Micromeister has posted, the really thin stuff can be cut with scissors, but that's more in the modroc realm.

You can cut it by hand with a Dremel or a saw; stationary tools like a band saw or jig saw are a bit easier.

Regardless, the stuff makes a horrible mess, and as someone else said, you don't want to inhale the dust. Protective eyewear and a respirator (not a paper mask, but one that fits more tightly) are both strongly recommended.

-Kevin

 

[Micromeister]

Kevin: has it ScrapDaddy:

Another is to use a Band or table saw with a vacuum collection system...Along with the respirator and safety glasses.
Further these personal safety equipment devices should be used with just about all the composite building materials included CF, fibreglass cloth and epoxies.
Personally I use G10-FR4 flame-retardant Garolite where garolite is desired, but you really should be getting off these exotic materials and try standard material composites you'll be amazed at the strength and stresses simple Basswood/paper or balsa/paper composites have over these heavier exotic material at a fraction of the cost.

 

[troj]

you'll be amazed at the strength and stresses simple Basswood/paper or balsa/paper composites have over these heavier exotic material at a fraction of the cost.

There's a lot of truth to that statement.

We've flown three rockets in the several hundred pound range with fins made from....1/4" floor underlayment and a thin layer of fiberglass. When the Pershing II came in ballistic, it threw one of the fins over 100 feet. The fin has a few scuffs on it, and that's it -- we could use it again tomorrow, if we wanted to. BTW, those fins were each held on with 3 stainless steel bolts.

I have a rocket (hasn't flown yet) which sims to Mach 1.6 with fins made of the same layup -- two layers of 1/4" floor underlayment with a layer of 3oz fiberglass in the middle. Light, inexpensive and very stiff.

Balsa, for its weight, is amazing stuff. There are amazingly thin plywoods available, and baltic birch plywood is great. All much easier to work with than G10, and just as importantly, much easier to get a good bond on.

Yes, I have rockets with G10 fins. It has its place in the world. But, as a general rule, I find it annoying to deal with.

-Kevin

 

[GregGleason]

... Balsa, for its weight, is amazing stuff. There are amazingly thin plywoods available, and baltic birch plywood is great. All much easier to work with than G10 ...

-Kevin

Compare the density of balsa to G-10: it's over 14 times as dense for the same volume!

G-10 is strong, but it is HEAVY. Because of that (and because it is difficult to work with), you only want to use G-10 when nothing else will work. In most cases, if you need that level of strength, you can get there with composite layups with lightweight cores.

Greg

 

[ScrapDaddy]

Compare the density of balsa to G-10: it's over 14 times as dense for the same volume!

G-10 is strong, but it is HEAVY. Because of that (and because it is difficult to work with), you only want to use G-10 when nothing else will work. In most cases, if you need that level of strength, you can get there with composite layups with lightweight cores.

Greg

But in the places where we use 1/8 balsa do we ever use 1/8 G10? Nope we use .0062" G10

 

[GregGleason]

But in the places where we use 1/8 balsa do we ever use 1/8 G10? Nope we use .0062" G10

I did not realize that you could get G-10 at 0.16mm thick. Who sells that?

Greg

 

[THier]

Something to think about,,, It is amazing how quick fiber glass will dull cutting edges. Hardened edges (carbide, diamond ect) will help,, but if you are not using hardened cutting edges, expect the tool to dull quickly. Quicker than cutting steel. I cut with a band saw, but the blade is done when I am.

Just saying.
Tom

 

[Micromeister]

I did not realize that you could get G-10 at 0.16mm thick. Who sells that?

Greg

Greg:
McMaster-Carr has G10-FR4 Garolite as thin as .005" in 12" x 12" or 24" x 36" sheets #1331T23 or #1331T57.

While ScrapDaddy is quoting an incorrect thickness .020 or .025" might well be used in place of 1/8" balsa. but I'd still consider .032" Balsa laminated both sides with .0156" aircraft 3-ply. Which would be considerably lighter yet just as strong at .0632" in thickness.

I gotta tell ya ScrapDaddy: Your really barking up a misguided tree unless you start really looking at these super light weight wood composites for you smaller, lighter machbuster type builds.

While G10 has it's purpose, building light, strong models just isn't it LOL!!! I used to use a lot of .005" and .010" G10-FR4 on flyaway competition models because of it's super thin profile, but there are other ways to go even with that.

 

[GregGleason]

Greg:
McMaster-Carr has G10-FR4 Garolite as thin as .005" in 12" x 12" or 24" x 36" sheets #1331T23 or #1331T57.

Thanks John. I didn't realize that McMaster-Carr had the very thin G-10/FR4, and pricey too at nearly $10 for 12 x 12 sheet!

I got a sheet of 1/32" about a year ago from them and I am surprised at the amount of flex at that thickness (more than I desired). I think you would have stiffer plate if you placed 3 sheets of paper between 6oz carbon fiber layup, IMHO. Thin, light, and not much flex. I may have to try that sometime ... in my free time. :roll:

Greg

 

[blackjack2564]

do you guys have any household tips that don't require a power tool?

Yep....hacksaw or hacksaw blade, preferably a metal cutting blade.

I have reshaped fins already epoxied on airframes this way.

Very little dust and can be cut wet if need be.

After cutting, tape all fins together and sand edges to get all exactly the same. Just like you do when free form cutting balsa fins.

 

[ScrapDaddy]

Greg:
McMaster-Carr has G10-FR4 Garolite as thin as .005" in 12" x 12" or 24" x 36" sheets #1331T23 or #1331T57.

While ScrapDaddy is quoting an incorrect thickness .020 or .025" might well be used in place of 1/8" balsa. but I'd still consider .032" Balsa laminated both sides with .0156" aircraft 3-ply. Which would be considerably lighter yet just as strong at .0632" in thickness.

I gotta tell ya ScrapDaddy: Your really barking up a misguided tree unless you start really looking at these super light weight wood composites for you smaller, lighter machbuster type builds.

While G10 has it's purpose, building light, strong models just isn't it LOL!!! I used to use a lot of .005" and .010" G10-FR4 on flyaway competition models because of it's super thin profile, but there are other ways to go even with that.

These are fOr the blades on a MPR heli-roc I'm working on

 

[jadebox]

These are fOr the blades on a MPR heli-roc I'm working on

I'd be concerned about using something hard like G10 for the blades.

Have you thought of using something like foam or balsa? Neither would be as durable as G10, but the blades would probably just break if they hit something rather than cause damage. Of course, they'd probably have to be replaced or repaired after each flight.

-- Roger

 

[Micromeister]

These are fOr the blades on a MPR heli-roc I'm working on

Rotors for helicopter recovery models really need to be airfoiled to create lift and as light as practical for the size model your building.
There are lots of good basic rotor designs out there for all kinds of models. I've made rotors from 1/2" x 6" to 6" x 60". Never used G10 in any of them.

Like I was saying earlier: You really need to slow down a bit, do some more reading and experiment a great deal more with Non-Exotic material composite material combinations.

 

[ScrapDaddy]

What did you use? Ply or basswoord?

 

[Micromeister]

What did you use? Ply or basswoord?

Mostly Sanded Balsa. Sanded to a really good airfoil or a combination of sanded airfoil and camber.

The Big 60" rotors were laminated SM Styrofoam/vinyl with an 1/8" tubular Graphite spar.

 

[troj]

The Big 60" rotors were laminated SM Styrofoam/vinyl with an 1/8" tubular Graphite spar.

I've seen rotors on a similar sized rocket (that flew on J motors) that were made in a style similar to balsa/tissue aircraft. Internal wood structure with a thin skin over it. Not the smoothest airfoil, but they worked and worked well.

-Kevin

 

[MarkII]

Rotors for heli-rocs also need to be extremely low in mass, because there is nothing to drive them but the onrushing air. A heli-roc with fiberglass rotors will be horribly heavy (think of how much spring you would need to lift those blades up to their deployed position, too) and it will drop quite far before it starts to auto-rotate, if it will even get started at all. Also consider how slow that rotation will be as those heavy rotors struggle to go around.

Long drop prior to the initiation of auto-rotation + slow rotational speed = not very much lift
​

Your heli-roc will most likely intersect with the ground before it is ever able to get going very well.

Mark K.

 

[Micromeister]

A great example of why heavy material aren't the best choice for Heli-rocs is the old estes Skywinder with it's plastic rotors and overweight plastic construction, while the thing did fly and rotate it really just barely could get out of its own way.

Mass is the ememy with all rockets but is expecially so with Gliders and Helirocs for as Mark mentioned there is nothing powering the rotors to turn other then air flow. We want the lightest possible combination of components that will hold together.

As Troj was saying even tissue and strut construction method works very well on larger rotor construction, the down side is recovery as the model touches down. stopping the rotors "before" they contact the ground can be the difference between another flight and going home for repair That consideration was a deciding point for me between that type consturction and slightly heavier SM Styrofoam/Vinyl combination.

 

[troj]

As Troj was saying even tissue and strut construction method works very well on larger rotor construction, the down side is recovery as the model touches down. stopping the rotors "before" they contact the ground can be the difference between another flight and going home for repair That consideration was a deciding point for me between that type consturction and slightly heavier SM Styrofoam/Vinyl combination.

C'mon, where's your sense of adventure? It's so much fun to have to do repairs after every flight...

You do raise a good point -- durability is a factor. That doesn't mean overbuild -- the styrofoam/vinyl rotors that Micro referenced are a good example of building with enough strength without going overboard.

There is a strong tendency in this hobby to over-engineer and over-build, especially as rockets get larger. It's not necessary, and can quickly add labor and expense, without doing much to improve flight and recovery reliability.

-Kevin

 

[MarkII]

One of the workshops at NARCON 2010 was on "D Helicopters" and it was presented by our current NAR president. He conveyed a great deal of useful information to the large group that attended, which included this total heliroc newbie. It was where I gained the insight about the rotors needing to be low in mass. I also received another interesting nugget there about the rotors, and I do hope that I am summarizing it accurately. He said that due to the relatively slow rotational speed of helicopter rockets, putting airfoils into the rotors does very little (or even nothing) to improve the lift that they generate. He said that as long as the rotors had the proper "twist" (incidence that varies along their length), then flat, thin (as thin as practical) rotors are probably the best option. The effort spent on airfoiling them could be better spent on improving the speed in which they are deployed (lifted up into position), getting them to initiate auto-rotation quickly (putting the right amount of incidence along the innermost third of the blades) and getting them to rotate faster (keeping the rotors light in weight and minimizing the friction in the hub). I think that I have that right, but my apologies in advance if I happen to have misstated anything.

He did show several actual helicopter rockets, including some flown at the Internats. I briefly looked at a rotor of one model up close at the end of the presentation, and if there was any airfoil in it, I sure couldn't see it. The model was designed to boost on a D motor, and the long, narrow rotors were made from, by all appearances, 1/32" thick balsa. I don't believe that it had any reinforcement along most of the length.

Mark K.

 

[Micromeister]

One of the workshops at NARCON 2010 was on "D Helicopters" and it was presented by our current NAR president. He conveyed a great deal of useful information to the large group that attended, which included this total heliroc newbie. It was where I gained the insight about the rotors needing to be low in mass. I also received another interesting nugget there about the rotors, and I do hope that I am summarizing it accurately. He said that due to the relatively slow rotational speed of helicopter rockets, putting airfoils into the rotors does very little (or even nothing) to improve the lift that they generate. He said that as long as the rotors had the proper "twist" (incidence that varies along their length), then flat, thin (as thin as practical) rotors are probably the best option. The effort spent on airfoiling them could be better spent on improving the speed in which they are deployed (lifted up into position), getting them to initiate auto-rotation quickly (putting the right amount of incidence along the innermost third of the blades) and getting them to rotate faster (keeping the rotors light in weight and minimizing the friction in the hub). I think that I have that right, but my apologies in advance if I happen to have misstated anything.

He did show several actual helicopter rockets, including some flown at the Internats. I briefly looked at a rotor of one model up close at the end of the presentation, and if there was any airfoil in it, I sure couldn't see it. The model was designed to boost on a D motor, and the long, narrow rotors were made from, by all appearances, 1/32" thick balsa. I don't believe that it had any reinforcement along most of the length.

Mark K.

Mark:
I totally agree with Trip's usual presentations on HD, but you must also consider exactly what was being said. Thin as possible is the optimum word. On many very thin material rotors you can't really see the airfoil if it is more or less molded in. Many of the HD models the internat flyers use are all internal rotors tucked inside very light fiberglass airframes. These models with their super thin & fragile rotors are a far cry for the main-stay of helirocs flown here in the US today ie Roto-rocs and Rose-a-Rocs. Looking at some of the HD models I fly it wouldn't look like they had a sanded airfoil at all, but it is there. In many thinner rotor materials the Twist your speaking of is more or less in intrical part of the airfoil of the rotors. The trick is to get them all twisted, balanced and spinning the same. Incidence is another measure, as is camber. I love buliding Helo's but their is much more to it than just the thinness of the rotor. The Plane on which the rotor disc rotates, rotor tip angle and deployment configuration all have huge impact on duration.